This contract is for a Registry and Repository for Antiphospholipid Syndrome (APS) that will enable investigators to identify basic immunological and genetic abnormalities, pathophysiological mechanisms contributing to thrombosis, fetal loss, and other clinical manifestations of APS. In addition, the Registry will be a key resource for projects aimed at improving methods of diagnosis and evaluating more effective and safer methods of treatment and prophylaxis. The registry will collect and update clinical, demographic, and laboratory data on patients with APS, asymptomatic patients with antiphospholipid antibodies, and certain individuals with serological and/or clinical features that fall within an expanded concept of APS. The availability of new classification criteria will allow resolution of the problems associated with disease heterogeneity and better comparisons among clinical research projects. The registry is a multi-center, multi-speciality, collaborative project involving a group of leading APS investigators (rheumatologists, hematologists, neurologists and obstetricians) at 8 academic medical centers.